Endogenous melatonin has numerous physiological roles on modulating the function of different organs. Recent studies revealed oncostatic and protective effects of this molecule on tumor development. In this study, we examined the impact of melatonin and key underlying mechanisms on stemness, morphology, invasiveness and viability of SKOV3 ovarian cancer cells in different types of extracellular matrix.

Cell viability was evaluated by MTT Assay. Colony-forming assay was performed by seeding 4×10³ cells on different matrices in six well-plate. The percentage of cancer stem like cells was determined by flow cytometric assay after applying antibodies against stemness markers, CD133 and CD44. Different types of extracellular matrix including fibronectin, gelatin, collagen and matrigel were applied to incubate the cells in the presence of melatonin. Downstream gene expressions including VEGF and E-cadherin were determined by Real-time PCR.

Melatonin (0.1mM) decreased the percentage of viable cells up to 61.79±8.2% (p<0.05). Colony formation assay revealed the significant impact of melatonin in inhibition of colony formation in these cells. The maximum effect was shown in the cells incubated with melatonin on gelatin (p<0.05). Identification of stemness markers showed that applying matrigel caused significant increase in the percentage of cancer stem like cells compared to other types of extracellular matrix (p<0.05). However melatonin slightly diminished the number of stem cell like cells in all incubated matrices. Our results from gene expression assays revealed that melatonin induced a marked increase in E-cadherin along with decrease in VEGF expression levels (p<0.05).

Our results suggest that interaction between ovarian cancer cells and neighboring matrices determines the subsequent anti invasive activities of melatonin.